You may want to change Week # (from 53 to 1) --
only for those days belonging to Week 53.
The calc could be like this (based on Sample Superstore):
IF DATEPART('week', [Order Date]) = 53
THEN DATEADD('day', DATEDIFF('day', [Order Date], DATEADD('year', 1, DATETRUNC('year', [Order Date]))), [Order Date])
ELSE [Order Date]
If you take a Discrete Week aggregate from the above date, Week 53 becomes Week 1.
Even if it fits your discrete week # scenario, other aggregates on this field would fail.
Hope it could help anyway.